BACK TOTOP Browse A-ZSearchBrowse A-ZABCDEFGHIJKLMNOPQRSTUVWXYZ0-9 E-mail FormEmail ResultsName:Email address:Recipients Name:Recipients address:Message: Print-FriendlyBookmarksbookmarks-menuEEGElectroencephalogram; Brain wave test; Epilepsy - EEG; Seizure - EEGAn electroencephalogram (EEG) is a test to measure the electrical activity of the brain. How the Test is Performed The test is done by an electroencephalogram technologist in your doctor's office or at a hospital or laboratory.The test is done in the following way:You lie on your back on a bed or in a reclining chair. Flat metal disks called electrodes are placed all over your scalp. The disks are held in place with a sticky paste. The electrodes are connected by wires to a recording machine. The machine changes the electrical signals into patterns that can be seen on a monitor or drawn on paper. These patterns look like wavy lines. You need to lie still during the test with your eyes closed. This is because movement can change the results. You may be asked to do certain things during the test, such as breathe fast and deeply for several minutes or look at a bright flashing light. You may be asked to sleep during the test. If your doctor needs to monitor your brain activity for a longer period, an ambulatory EEG will be ordered. In addition to the electrodes, you will wear or carry a special recorder for up to 3 days. You will be able to go about your normal routine as the EEG is being recorded. Or, your doctor may ask you to stay overnight in a special EEG monitoring unit where your brain activity will be monitored continuously. How to Prepare for the Test Wash your hair the night before the test. DO NOT use conditioner, oils, sprays, or gel on your hair. If you have a hair weave, ask your health care provider for special instructions.Your provider may want you to stop taking certain medicines before the test. DO NOT change or stop taking any medicines without first talking to your provider. Bring a list of your medicines with you.Avoid all food and drinks containing caffeine for 8 hours before the test.You may need to sleep during the test. If so, you may be asked to reduce your sleep time the night before. If you are asked to sleep as little as possible before the test, DO NOT eat or drink any caffeine, energy drinks, or other products that help you stay awake.Follow any other specific instructions you are given. How the Test will Feel The electrodes may feel sticky and strange on your scalp, but should not cause any other discomfort. You should not feel any discomfort during the test. Why the Test is Performed Brain cells communicate with each other by producing tiny electrical signals, called impulses. An EEG measures this activity. It can be used to diagnose or monitor the following health conditions:Seizures and epilepsy SeizuresA seizure is the physical changes in behavior that occurs during an episode of abnormal electrical activity in the brain. The term "seizure" is often...ImageRead Article Now Book Mark Article EpilepsyEpilepsy is a brain disorder in which a person has repeated seizures over time. Seizures are episodes of uncontrolled and abnormal firing of brain c...ImageRead Article Now Book Mark Article Abnormal changes in body chemistry that affect the brain Brain diseases, such as Alzheimer disease Alzheimer diseaseDementia is a loss of brain function that occurs with certain diseases. Alzheimer disease (AD) is the most common form of dementia. It affects memo...ImageRead Article Now Book Mark Article Confusion ConfusionConfusion is the inability to think as clearly or quickly as you normally do. You may feel disoriented and have difficulty paying attention, remembe...ImageRead Article Now Book Mark Article Fainting spells or periods of memory loss that cannot be explained otherwise Head injuries Head injuriesA head injury is any trauma to the scalp, skull, or brain. Head injury can be either closed or open (penetrating). A closed head injury means you rec...ImageRead Article Now Book Mark Article Infections Tumors EEG is also used to:Evaluate problems with sleep (sleep disorders) Sleep disordersSleep disorders are problems with sleeping. These include trouble falling or staying asleep, falling asleep at the wrong times, too much sleep, and ...ImageRead Article Now Book Mark Article Monitor the brain during brain surgery An EEG may be done to show that the brain has no activity, in the case of someone who is in a deep coma. It can be helpful when trying to decide if a person is brain dead.EEG cannot be used to measure intelligence. Normal Results Brain electrical activity has a certain number of waves per second (frequencies) that are normal for different levels of alertness. For example, brain waves are faster when you are awake and slower in certain stages of sleep.There are also normal patterns to these waves. Note: A normal EEG does not mean that a seizure did not occur. What Abnormal Results Mean Abnormal results on an EEG test may be due to:Abnormal bleeding (hemorrhage) An abnormal structure in the brain (such as a brain tumor) Brain tumorA brain tumor is a group (mass) of abnormal cells that grow in the brain. This article focuses on primary brain tumors in children.ImageRead Article Now Book Mark Article Tissue death due to a blockage in blood flow (cerebral infarction) Drug or alcohol abuse Head injury Migraines (in some cases) Seizure disorder (such as epilepsy) Sleep disorder (such as narcolepsy) NarcolepsyNarcolepsy is a nervous system problem that causes extreme sleepiness and attacks of daytime sleep.ImageRead Article Now Book Mark Article Swelling of the brain (edema) Risks An EEG test is very safe. The flashing lights or fast breathing (hyperventilation) required during the test may trigger seizures in those with seizure disorders. The provider performing the EEG is trained to take care of you if this happens.HyperventilationHyperventilation is rapid and deep breathing. It is also called overbreathing, and it may leave you feeling breathless.Read Article Now Book Mark Article Open ReferencesReferencesDeluca GC, Griggs RC. Approach to the patient with neurologic disease. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 368.Hahn CD, Emerson RG. Electroencephalography and evoked potentials. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 35.AllVideoImagesTogBrain - illustration The major areas of the brain have one or more specific functions.BrainillustrationBrain wave monitor - illustration The brainstem auditory evoked response test (BAER), is performed to help diagnose nervous-system abnormalities, hearing losses (especially in low-birth weight newborns), and to assess neurologic functions. The test focuses on changes and responses in brain waves. The brain waves are stimulated by a clicking sound to evaluate the central auditory pathways of the brainstem. Brain wave monitorillustrationBrain - illustration The major areas of the brain have one or more specific functions.BrainillustrationBrain wave monitor - illustration The brainstem auditory evoked response test (BAER), is performed to help diagnose nervous-system abnormalities, hearing losses (especially in low-birth weight newborns), and to assess neurologic functions. The test focuses on changes and responses in brain waves. The brain waves are stimulated by a clicking sound to evaluate the central auditory pathways of the brainstem. Brain wave monitorillustration Tests for EEG EEGRelated Information Epilepsy(Condition)Confusion(Symptoms)Head injury - first aid(Injury)Sleep disorders(Condition)Decreased alertness(Symptoms)Seizures(Symptoms)Brain tumor - children(Condition)Brain abscess(Condition)Encephalitis(Condition)Narcolepsy(Condition)Epilepsy(In-Depth)Brain tumors - primary(In-Depth)Viral encephalitis (In-Depth) Review Date: 2/4/2020 Reviewed By: Amit M. Shelat, DO, FACP, FAAN, Attending Neurologist and Assistant Professor of Clinical Neurology, Stony Brook University School of Medicine, Stony Brook, NY. Review provided by VeriMed Healthcare Network. Internal review and update on 06/03/2021 by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- © 1997- All rights reserved. A.D.A.M. content is best viewed in IE9 or above, Firefox and Google Chrome browser.Content is best viewed in IE9 or above, Firefox and Google Chrome browser.